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First paragraph of introduction: On 20 July 2004 a single Asian tapeworm (Bothriocephalus acheilognathi) was collected from the intestine of a roundtail chub (Gila robusta) in the Yampa River in Dinosaur National Monument in northwestern Colorado. This fish (274 mm TL) was collected at river mile 24 and dissected in the field. A single tapeworm was removed from the intestine and preserved in ethanol. The tapeworm was later identified in the laboratory as B. acheilognathi by its characteristic arrow-shaped scolex (Poole et al. 1984). This is the 1st recorded incidence of Asian tapeworm infecting fish in the Yampa River drainage. Published in Western North American Naturalist, volume 65, issue 3, on pages 403 - 404,...
ms have reduced distribution of the endangered Colorado pikeminnow Ptychocheilus lucius in the upper Colorado River basin: low-head diversion dams blocked upstream passage and large dams inundated free-flowing segments and cooled downstream reaches with deep-water releases. To date, range restoration efforts in the Colorado and Gunnison Rivers have focused on building fish ladders around diversion dams to allow recolonization of upstream reaches. Upstream thermal suitability for this warmwater cyprinid was assessed using temperature data and existing distributional information from river reaches where Colorado pikeminnow movements were unrestricted. Among-site thermal regime comparisons were made using mean annual...
Larval and juvenile Colorado pikeminnow (Ptychocheilus lucius) use shallow, low-velocity, channel-margin areas (backwaters) as nursery habitats. It is hypothesized that within-day flow fluctuations caused by hydropower operations can directly affect the suitability of such habitats by altering water temperature and habitat geometry. Despite the importance of backwaters to juvenile fishes, there is a lack of established approaches for modelling how river management affects these habitats. Here, we describe a physical habitat model that predicts the effects of mainstem flow variation on backwater temperature, geometry and invertebrate availability. We specifically modelled these effects on habitat in a portion of...
Understanding how altered flow regimes mediate interactions among native and nonnative species is necessary for the conservation of aquatic systems. Anthropogenic alteration of natural flows and establishment of nonnative fishes coincided with near extirpation of Colorado pikeminnow (Ptychocheilus lucius) from the San Juan River, NM, USA. Despite major efforts to re-establish this species, recruitment of young individuals into the adult population has not been documented in several decades. A potential reason for apparent recruitment failure is that modified flow regimes and nonnative species have affected reproductive success of native prey, thus limiting potentially critical resources for young (
Twelve wild adult Colorado pikeminnow (Ptychocheilus lucius), captured in the tailwaters of Taylor Draw Dam on the White River, Colorado, were implanted with radio transmitters and their movement patterns monitored from 1992 to 1994. The spawning migration of these fish was extensive. In 1993, the only full year of the study, the fish migrated an average of 658 km from the White River to spawning sites in the Yampa or Green rivers and back to the White River. Eight of these fish were translocated in the river upstream of the dam in April 1993. These fish and the 4 others below the dam remained in the river until May 1993. All 12 had migrated down the White River to spawning sites in the Green and Yampa rivers by...
The goal of this study is to define the baseflow needs of endangered fish populations in the Yampa River. The approach taken was to simulate habitat availability associated with several low flow scenarios and relate changes in habitat availability to habitat use by endangered fishes.
We evaluated the role of major tributary streams for endangered fish recovery using a matrix approach based on quantitative information. However, the need for ranking tributaries for direct and indirect contributions (i.e., assignment of high, medium or low importance) required a more subjective approach. Some streams differed in actual and potential importance because barriers deny fish access to suitable habitat. We have not assigned relative importance to the different types of contributions; to a large extent that may involve policy issues better addressed by the Recovery Program.
nthropogenic selenium contamination of aquatic ecosystems was first associated with cooling reservoirs of coal-fired power plants in the late 1970s, and later with drainage water from agricultural irrigation activities in the 1980s. In the 1990s, selenium contamination has been raised as a concern in the recovery of currently endangered fish in the Colorado River system. Widespread contamination from seleniferous drain waters from agriculture has been documented in the upper and lower Colorado River basins. Historically, irrigation started in the upper Colorado River basin in the late 1880s. In the 1930s, selenium concentrations in various drains, tributaries, and major rivers in the upper and lower Colorado River...
In the White River basin, water demand has increased with human development. Water development projects impact White River hydrology and sediment transport which can, in turn, affect resident Colorado pikeminnow populations. The objectives for this study were: 1) to compile historical biological, hydrological and physical data for the White River, 2) to analyze physical, chemical and biological features of the White River important to endangered fishes and, 3) to identify parameters for long-term monitoring to insure these features are maintained. We examined physical, chemical and biological characteristics during three development periods in the UCRB: early (1895-1945), middle (1946-1984) and post Taylor Draw...
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The Colorado River Basin provides habitat for 14 native fish, including four endangered species protected under the Federal Endangered Species Act of 1973 - Colorado pikeminnow (Ptychocheilus lucius), razorback sucker (Xyrauchen texanus), bonytail (Gila elegans), and humpback chub (Gila cypha). These endangered fish species once thrived in the Colorado River system, but water-resource development, including the building of numerous diversion dams and several large reservoirs, and the introduction of nonnative fish, resulted in large reductions in the numbers and range of the four species. Knowledge of sediment dynamics in river reaches important to specifc life-stages of the endangered fishes is critical to understanding...
Alteration of natural flow regimes by river regulation affects fish distribution and assemblage structure, but causative pathways are not always direct and may go unrecognized. The Colorado River population of the endangered Colorado pikeminnow, Ptychocheilus lucius, suffers from low rates of recruitment and reduced carrying capacity. We hypothesized that availability of prey fish for this large-bodied native piscivore may, in part, be limited by reduced standing crops of periphyton and macroinvertebrates resulting from accumulation of fine sediment in the riverbed. We stratified the 373-km-long study area into 11 strata and sampled various physical and biological parameters in runs and riffles of three randomly...
Analysis of field data and development and application of a dynamic model indicate that the processes that control the number and distribution of age-0 Colorado pikeminnow in the middle Green River are poorly understood. Colorado pikeminnow are a federally endangered species endemic to the Colorado River basin that utilize backwaters during their larval stage. The present agency-mandated field sampling program for backwater habitats may be inadequate because it takes place at a time when the model predicts that most larval fish have drifted beyond the study area. The model predicts that water releases from Flaming Gorge Dam have a large potential effect on larval drift, because high releases at the time of drift...
Evidence for sexual size dimorphism (SSD) and its possible causes were examined in the endangered Colorado pikeminnow Ptychocheilus lucius, a large, piscivorous, cyprinid endemic to the Colorado River system of North America. Individuals representing 18?24% of the upper Colorado River population were captured, measured, sexed and released in 1999 and 2000. Differing male and female total length-(LT) frequency distributions revealed SSD with females having greater mean and maximum sizes than males. Although both sexes exhibit indeterminate post-maturity growth, growth trajectories differed. The point of trajectory divergence was not established, but slowed male growth might coincide with the onset of maturation....
    map background search result map search result map Summary of Fluvial Sediment Collected at Selected Sites on the Gunnison River in Colorado and the Green and Duchesne Rivers in Utah, Water Years 2005-2008 Collection of Asian tapeworm ( Bothriocephalus acheilognathi ) from the Yampa River, Colorado Collection of Asian tapeworm ( Bothriocephalus acheilognathi ) from the Yampa River, Colorado Summary of Fluvial Sediment Collected at Selected Sites on the Gunnison River in Colorado and the Green and Duchesne Rivers in Utah, Water Years 2005-2008